Research Article |
Corresponding author: Mohd Zacaery Khalik ( zacaery12@gmail.com ) Academic editor: Frank Köhler
© 2019 Mohd Zacaery Khalik, Kasper P. Hendriks, Jaap J. Vermeulen, Menno Schilthuizen.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Khalik MZ, Hendriks KP, Vermeulen JJ, Schilthuizen M (2019) Conchological and molecular analysis of the “non-scaly” Bornean Georissa with descriptions of three new species (Gastropoda, Neritimorpha, Hydrocenidae). ZooKeys 840: 35-86. https://doi.org/10.3897/zookeys.840.33326
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The Bornean representatives of the genus Georissa (Hydrocenidae) have small, dextral, conical, calcareous shells consisting of ca. three teleoconch whorls. Our recent study on the Georissa of Malaysian Borneo has revealed high intra- and inter-specific variation in the “scaly” group (a group of species with striking scale-like surface sculpture). The present study on the “non-scaly” Georissa is the continuation of the species revision for the genus. The “non-scaly” species are also diverse in shell sculptures. This informal group comprises Georissa with subtle spiral and/or radial sculpture. The combination of detailed conchological assessment and molecular analyses provides clear distinctions for each of the species. Conchological, molecular, and biogeographic details are presented for 16 species of “non-scaly” Georissa. Three of these are new to science, namely Georissa corrugata sp. n., Georissa insulae sp. n., and Georissa trusmadi sp. n.
Gastropods, limestone, morphology, phylogenetic, species delimitation, Sabah, Sarawak Malaysian Borneo
The genus Georissa Blanford, 1864 (Hydrocenidae) comprises minute terrestrial snails, generally characterized by a small, dextral, conical, calcareous shell with ca. three teleoconch whorls (
Until recently, simple conchological analyses have been the main approach to describe and study the species of Bornean Georissa. In our recent systematic study of the “scaly” Georissa (see
In this paper, the second part of our work on the Bornean Georissa, we apply the same approach of combining information from multiple datasets to 16 species of Bornean Georissa that belong to the informal “non-scaly” group, characterised mainly by weak to strong spiral and/or radial sculptures without conspicuous scale-like sculpture on the shell. We also present the phylogenetic relationships among all Bornean Georissa and their distribution. We describe three species new to science, namely Georissa corrugata sp. n., Georissa insulae sp. n., and Georissa trusmadi sp. n.
We examined collection material from:
JJV Jaap Vermeulen (personal collection).
We conducted series of fieldwork at limestone outcrops in Malaysian Borneo between September 2015 and October 2018. We searched for living Georissa on the limestone walls and rocks, loose organic matter, and living leaves. The collected specimens were directly sorted and stored in sample tubes with ~96% ethanol. Ca. 5 liters of soil and leaf litter were sampled at every sampling location, which were later sieved and soaked in water to collect the empty shells by flotation (
Microscopy. The shells were observed under a stereomicroscope for species identification and detailed examination at 40–100 × magnification. The 2-dimensional images of the individual shell of each Georissa species were captured in three views, namely apertural (aperture as the frontal view), side (the right side of the shell as the frontal view), and rear (umbilical region as the frontal view) views, using AxioCamMRc5, Zeiss PlanApo S 1.0 × FWD 60.0mm lenses. The apertural view images of each individual shell were then measured to obtain shell height (SH), shell width (SW), aperture height (AH), and aperture width (AW).
Scanning electron microscopy (SEM). We selected a representative adult shell of each species for detailed character examination by using scanning electron microscopy. The shells were first cleaned in sodium hypochloride, dried and then sputter-coated with Pd/Pt coating agent. We used a JEOL JSM-6480LV machine for SEM imaging to obtain detailed shell characters of the teleoconch and protoconch.
Micro-computed tomography (µ-CT). The µ-CT scanning was carried out using an Xradia 520 Versa X-ray Microscope (see Suppl. material
DNA extraction. The sample preparation prior to DNA extraction procedure followed the method from
DNA amplification. We used the primer pairs LR-J-12887 5’-CCGGTCTGAACTCAGATCACGT-3’ (forward) and LR-N-13398 5’-CGCCTGTTTAACAAAAAACAT-3’ (reverse) (
DNA Sequencing. PCR products were sent to BaseClear B.V. (Leiden, The Netherlands) and Sanger sequenced in forward and reverse directions using the ABI3730XL sequencer, Life Technologies.
Sequence data. From GenBank, we downloaded 16S and CO1 mtDNA sequences of representatives of the “scaly” group species, G. gomantonensis (
Sequence alignment. The 16S and CO1 mtDNA sequences were aligned to their respective genes using default parameters of MUSCLE (
Phylogenetic inference. The alignment of CO1 mtDNA was set to invertebrate mitochondrial genetic code at the third reading frame. The best fit nucleotide substitution models of the concatenated 16S and CO1 sequence alignment was determined using ModelFinder (
Phylogenetic analysis. We performed a maximum likelihood analysis using the concatenated alignment using GTR+F+R4 nucleotide substitution model with ultrafast bootstrapping (5000 replicates) (
No. | Species | Voucher No. | Species name_sequence origin_location Town/District/Division, State. GPS coordinate | GenBank Accession No. | |
---|---|---|---|---|---|
16S | CO1 | ||||
1 | Georissa saulae (van Benthem Jutting, 1966) | BOR/MOL 2663-2667 | G.saulae_AY547385_Sinobang |
AY547385 ( |
n/a |
Batu Sinobang, Sabah. | |||||
04°48.04'N, 116°37.03'E | |||||
2 | Georissa saulae (van Benthem Jutting, 1966) | BOR/MOL 12770 | G.saulae_Sau-001_Pungiton |
MG982262 ( |
MK722149 |
Sepulut Valley, Gua Pungiton, Sabah. | |||||
04°42.41'N, 116°36.04'E | |||||
3 | Georissa saulae (van Benthem Jutting, 1966) | BOR/MOL 12770 | G.saulae_Sau-002_Pungiton |
MG982263 ( |
MK722150 |
Sepulut Valley, Gua Pungiton, Sabah. | |||||
04°42.41'N, 116°36.04'E | |||||
4 | Georissa filiasaulae Haase & Schilthuizen, 2007 | BOR/MOL 12768 | G.filiasaulae_002_Pungiton | MK411785 | MK505425 |
Sepulut Valley, Gua Pungiton, Sabah. | |||||
04°42.41'N, 116°36.04'E | |||||
5 | Georissa filiasaulae Haase & Schilthuizen, 2007 | BOR/MOL 12768 | G.filiasaulae_003_Pungiton | MK411786 | MK505426 |
Sepulut Valley, Gua Pungiton, Sabah. | |||||
04°42.41'N, 116°36.04'E | |||||
6 | Georissa filiasaulae Haase & Schilthuizen, 2007 | BOR/MOL 12768 | G.filiasaulae_005_Pungiton | MK411787 | MK505427 |
Sepulut Valley, Gua Pungiton, Sabah. | |||||
04°42.41'N, 116°36.04'E | |||||
7 | Georissa pachysoma Vermeulen & Junau, 2007 |
|
G.pachysoma_BSM2-01_Bukit Sarang | MK411789 | MK505443 |
Bukit Sarang, Bintulu, Sarawak. | |||||
02°39.31'N, 113°02.47'E | |||||
8 | Georissa pachysoma Vermeulen & Junau, 2007 |
|
G.pachysoma_BSM2-02_Bukit Sarang | MK411788 | MK505442 |
Bukit Sarang, Bintulu, Sarawak. | |||||
02°39.31'N, 113°02.47'E | |||||
9 | Georissa pachysoma Vermeulen & Junau, 2007 |
|
G.pachysoma_BSM2-03_Bukit Sarang | MK411791 | MK505441 |
Bukit Sarang, Bintulu, Sarawak. | |||||
02°39.31'N, 113°02.47'E | |||||
10 | Georissa pachysoma Vermeulen & Junau, 2007 |
|
G.pachysoma_BSM2-04_Bukit Sarang | MK411790 | MK505440 |
Bukit Sarang, Bintulu, Sarawak. | |||||
02°39.31'N, 113°02.47'E | |||||
11 | Georissa similis Smith, 1893 |
|
G.similis_E001_Batu Batangan | MK411792 | MK505446 |
Batu Batangan, Sabah. | |||||
05°27.61'N, 118°06.17'E | |||||
12 | Georissa similis Smith, 1893 |
|
G.similis_E002_Batu Batangan | MK411795 | MK505444 |
Batu Batangan, Sabah. | |||||
05°27.61'N, 118°06.17'E | |||||
13 | Georissa similis Smith, 1893 |
|
G.similis_E003_Batu Batangan | MK411793 | n/a |
Batu Batangan, Sabah. | |||||
05°27.61'N, 118°06.17'E | |||||
14 | Georissa similis Smith, 1893 |
|
G.similis_E004_Batu Batangan | MK411794 | MK505445 |
Batu Batangan, Sabah. | |||||
05°27.61'N, 118°06.17'E | |||||
15 | Georissa bangueyensis Smith, 1895 |
|
G.bangueyensis_KPH01627.01_NewLocation1 | MK403002 | MH254770 |
New Location 1, Kinabatangan River, Sabah | |||||
05°27.40'N, 118°08.76'E | |||||
16 | Georissa bangueyensis Smith, 1895 |
|
G.bangueyensis_KPH01627.02_NewLocation1 | MK402999 | MH254645 |
New Location 1, Kinabatangan River, Sabah | |||||
05°27.40'N, 118°08.76'E | |||||
17 | Georissa bangueyensis Smith, 1895 |
|
G.bangueyensis_KPH01589.01_NewLocation1 | MK402996 | n/a |
New Location 1, Kinabatangan River, Sabah | |||||
05°27.40'N, 118°08.76'E | |||||
18 | Georissa bangueyensis Smith, 1895 |
|
G.bangueyensis_KPH01589.02_NewLocation1 | MK402993 | MH254230 |
New Location 1, Kinabatangan River, Sabah | |||||
05°27.40'N, 118°08.76'E | |||||
19 | Georissa bangueyensis Smith, 1895 |
|
G.bangueyensis_KPH01589.05_NewLocation1 | MK402998 | MH254559 |
New Location 1, Kinabatangan River, Sabah | |||||
05°27.40'N, 118°08.76'E | |||||
20 | Georissa bangueyensis Smith, 1895 |
|
G.bangueyensis_KPH01594.01_NewLocation1 | MK402997 | MH254416 |
New Location 1, Kinabatangan River, Sabah | |||||
05°27.40'N, 118°08.76'E | |||||
21 | Georissa flavescens Smith, 1895 | BOR/MOL 7660 | G.flavescens_KPH02157.12_Pangi | MK402995 | MH254340 |
Batu Pangi, Kinabatangan valley, Sabah. | |||||
05°32.01'N, 118°18.24'E | |||||
22 | Georissa flavescens Smith, 1895 | BOR/MOL 7638 | G.flavescens_KPH02135.11_Pangi | MK402989 | MH254024 |
Batu Pangi, Kinabatangan valley, Sabah. | |||||
05°31.89'N, 118°18.37'E | |||||
23 | Georissa flavescens Smith, 1895 | BOR/MOL 7626 | G.flavescens_KPH02123.07_Tomanggong Besar | MK403001 | MH254706 |
Batu Tomanggong Besar, Kinabatangan valley, Sabah. | |||||
05°31.83'N, 118°18.26'E | |||||
24 | Georissa flavescens Smith, 1895 | BOR/MOL 7293 | G.flavescens_KPH01725.08_Tomanggong Besar | MK402992 | MH254160 |
Batu Tomanggong Besar, Kinabatangan valley, Sabah. | |||||
05°31.52'N, 118°18.41'E | |||||
25 | Georissa flavescens Smith, 1895 | BOR/MOL 7638 | G.flavescens_KPH02135.08_Pangi | MK402990 | MH254028 |
Batu Pangi, Kinabatangan valley, Sabah. | |||||
05°31.89'N, 118°18.37'E | |||||
26 | Georissa flavescens Smith, 1895 | BOR/MOL 7416 | G.flavescens_KPH01860.09_Tomanggong Besar | MK403003 | MH254769 |
Batu Tomanggong Besar, Kinabatangan valley, Sabah. | |||||
05°31.38'N, 118°17.89'E | |||||
27 | Georissa flavescens Smith, 1895 | BOR/MOL 7299 | G.flavescens_KPH01733.03_Tomanggong Besar | MK402994 | MH254313 |
Batu Tomanggong Besar, Kinabatangan valley, Sabah. | |||||
05°31.33'N, 118°18.06'E | |||||
28 | Georissa flavescens Smith, 1895 | BOR/MOL 7294 | G.flavescens_KPH01727.13_Tomanggong Besar | n/a | MH254614 |
Batu Tomanggong Besar, Kinabatangan valley, Sabah. | |||||
05°31.46'N, 118°18.14'E | |||||
29 | Georissa nephrostoma Vermeulen et al., 2015 |
|
G.nephrostoma_K001_Keruak | MK411797 | MK505439 |
Batu Keruak, Kinabatangan valley, Sabah. | |||||
05°32.291'N, 118°18.376'E | |||||
30 | Georissa nephrostoma Vermeulen et al., 2015 |
|
G.nephrostoma_K002_Keruak | MK411798 | n/a |
Batu Keruak, Kinabatangan valley, Sabah. | |||||
05°32.291'N, 118°18.376'E | |||||
31 | Georissa nephrostoma Vermeulen et al., 2015 |
|
G.nephrostoma_K003_Keruak | MK411800 | n/a |
Batu Keruak, Kinabatangan valley, Sabah. | |||||
05°32.291'N, 118°18.376'E | |||||
32 | Georissa nephrostoma Vermeulen et al., 2015 |
|
G.nephrostoma_K004_Keruak | MK411796 | n/a |
Batu Keruak, Kinabatangan valley, Sabah. | |||||
05°32.291'N, 118°18.376'E | |||||
33 | Georissa nephrostoma Vermeulen et al., 2015 |
|
G.nephrostoma_K005_Keruak | MK411799 | n/a |
Batu Keruak, Kinabatangan valley, Sabah. | |||||
05°32.291'N, 118°18.376'E | |||||
34 | Georissa xesta Thompson & Dance, 1983 | BOR/MOL 7258 | G.xesta_KPH02048.12_Materis | MK403000 | MH254698 |
Materis, Kinabatangan valley, Sabah. | |||||
05°31.39'N, 118°10'E | |||||
35 | Georissa xesta Thompson & Dance, 1983 | BOR/MOL 7303 | G.xesta_KPH01738.05_Ulu Resang | MK402991 | MH254122 |
Ulu Sungai Resang, Kinabatangan valley, Sabah. | |||||
05°30.67'N, 118°20.39'E | |||||
36 | Georissa xesta Thompson & Dance, 1983 | BOR/MOL 7311 | G.xesta_KPH01746.06_Ulu Resang | n/a | MH254082 |
Ulu Sungai Resang, Kinabatangan valley, Sabah. | |||||
05°31.16'N, 118°19.78'E | |||||
37 | Georissa hungerfordi Godwin-Austen, 1889 |
|
G.hungerfordi_G001_Mawah | MK411771 | n/a |
Gunong Mawah, Padawan/Penrissen, Sarawak. | |||||
01°16.15'N, 110°15.46'E | |||||
38 | Georissa hungerfordi Godwin-Austen, 1889 |
|
G.hungerfordi_G002_Mawah | MK411773 | n/a |
Gunong Mawah, Padawan/Penrissen, Sarawak. | |||||
01°16.15'N, 110°15.46'E | |||||
39 | Georissa hungerfordi Godwin-Austen, 1889 |
|
G.hungerfordi_G003_Mawah | MK411770 | MK505432 |
Gunong Mawah, Padawan/Penrissen, Sarawak. | |||||
01°16.15'N, 110°15.46'E | |||||
40 | Georissa hungerfordi Godwin-Austen, 1889 |
|
G.hungerfordi_G004_Mawah | MK411772 | n/a |
Gunong Mawah, Padawan/Penrissen, Sarawak. | |||||
01°16.15'N, 110°15.46'E | |||||
41 | Georissa hungerfordi Godwin-Austen, 1889 |
|
G.hungerfordi_I001_Regu | MK411775 | MK505428 |
Regu, Padawan/Penrissen, Sarawak. | |||||
01°12.82'N, 110°16.82'E | |||||
42 | Georissa hungerfordi Godwin-Austen, 1889 |
|
G.hungerfordi_I002_Regu | MK411774 | MK505438 |
Regu, Padawan/Penrissen, Sarawak. | |||||
01°12.82'N, 110°16.82'E | |||||
43 | Georissa hungerfordi Godwin-Austen, 1889 |
|
G.hungerfordi_I003_Regu | MK411777 | MK505437 |
Regu, Padawan/Penrissen, Sarawak. | |||||
01°12.82'N, 110°16.82'E | |||||
44 | Georissa hungerfordi Godwin-Austen, 1889 |
|
G.hungerfordi_I004_Regu | MK411776 | MK505436 |
Regu, Padawan/Penrissen, Sarawak. | |||||
01°12.82'N, 110°16.82'E | |||||
45 | Georissa hungerfordi Godwin-Austen, 1889 |
|
G.hungerfordi_H001_Sirat | MK411784 | MK505431 |
Gunong Sirat, Padawan/Penrissen, Sarawak. | |||||
01°12.42'N, 110°16.52'E | |||||
46 | Georissa hungerfordi Godwin-Austen, 1889 |
|
G.hungerfordi_H002_Sirat | MK411783 | MK505430 |
Gunong Sirat, Padawan/Penrissen, Sarawak. | |||||
01°12.42'N, 110°16.52'E | |||||
47 | Georissa hungerfordi Godwin-Austen, 1889 |
|
G.hungerfordi_H003_Sirat | MK411778 | MK505429 |
Gunong Sirat, Padawan/Penrissen, Sarawak. | |||||
01°12.42'N, 110°16.52'E | |||||
48 | Georissa hungerfordi Godwin-Austen, 1889 |
|
G.hungerfordi_H004_Sirat | MK411782 | n/a |
Gunong Sirat, Padawan/Penrissen, Sarawak. | |||||
01°12.42'N, 110°16.52'E | |||||
49 | Georissa hungerfordi Godwin-Austen, 1889 |
|
G.hungerfordi_F001_Duai | MK411780 | MK505435 |
Gunong Seduai, Padawan/Penrissen, Sarawak. | |||||
01°12.25'N, 110°17.00'E | |||||
50 | Georissa hungerfordi Godwin-Austen, 1889 |
|
G.hungerfordi_F002_Duai | MK411781 | MK505434 |
Gunong Seduai, Padawan/Penrissen, Sarawak. | |||||
01°12.25'N, 110°17.00'E | |||||
51 | Georissa hungerfordi Godwin-Austen, 1889 |
|
G.hungerfordi_F004_Duai | MK411779 | MK505433 |
Gunong Seduai, Padawan/Penrissen, Sarawak. | |||||
01°12.25'N, 110°17.00'E | |||||
52 | Georissa insulae sp. n. |
|
G.insulae_Man_001 | MK411801 | n/a |
Pulau Mantanani Besar, Sabah. | |||||
06°43.06'N, 116°20.50'E | |||||
53 | Georissa insulae sp. n. |
|
G.insulae_Man_002 | MK411803 | n/a |
Pulau Mantanani Besar, Sabah. | |||||
06°43.06'N, 116°20.50'E | |||||
54 | Georissa insulae sp. n. |
|
G.insulae_Man_003 | MK411804 | n/a |
Pulau Mantanani Besar, Sabah. | |||||
06°43.06'N, 116°20.50'E | |||||
55 | Georissa insulae sp. n. |
|
G.insulae_Man_004 | MK411802 | n/a |
Pulau Mantanani Besar, Sabah. | |||||
06°43.06'N, 116°20.50'E |
Species delimitation of the “non-scaly” group Bornean Georissa was carried out based on detailed examination of the shell characters which are exclusive to the group, combined with the molecular analyses. While morphological analysis is widely accepted for species identification in gastropods, this conventional way of species delimitation could become very challenging when applied to the genus Georissa which show high morphological variation within and between populations. For this reason, we applied a similar species delimitation approach as done in the “scaly” group Georissa (
CO1 genetic divergence was performed to determine the genetic distances between species of the “non-scaly” group Georissa. We conducted genetic distance analysis within and between species groups. We computed pairwise genetic distances of CO1 sequence alignment based on the nucleotide substitution model Kimura 2-parameter in MEGA v. 7.0.26 (
The “non-scaly” Georissa from Borneo are characterised by the simple spiral and/or radial sculpture on the shell, unlike the distinct scale-like structures of the “scaly” group. These two informal groups of Georissa could be used as an initial framework for future species identification. Previously,
Our previous work on the “scaly” group Bornean Georissa (
There is a similar confusion with G. borneensis, a name widely applied to both G. similis and G. corrugata sp. n. in the collection materials.
On the one hand, we find that “non-scaly” Georissa have strongly supported monophyletic groups with bootstrap and posterior output values in our phylogenetic analyses, ranging from 96–100 and 100, respectively. This corresponds to conchological characters of the respective taxa. On the other hand, we find G. xesta is paraphyletic. Discussions for each species treatment are in the Systematic part.
Species delimitation based solely on morphological analysis of this group of closely related minute gastropods could be challenging, especially when the studied taxa have high intra-specific variation (see
The CO1 genetic divergence (Table
Intra- and inter-specific divergence of partial CO1 sequences of nine species of the “non-scaly” Georissa.
Divergence within group | Number of specimens | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | ||
---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | G. gomantonensis | 0.00 | 2 | |||||||||
2 | G. filiasaulae | 0.00 | 3 | 0.24 | ||||||||
3 | G. hungerfordi | 0.05 | 11 | 0.21 | 0.22 | |||||||
4 | G. pachysoma | <0.01 | 4 | 0.22 | 0.25 | 0.20 | ||||||
5 | G. similis | <0.01 | 3 | 0.22 | 0.22 | 0.20 | 0.17 | |||||
6 | G. flavescens | 0.03 | 8 | 0.19 | 0.22 | 0.16 | 0.20 | 0.19 | ||||
7 | G. bangueyensis | <0.01 | 5 | 0.22 | 0.23 | 0.17 | 0.23 | 0.20 | 0.11* | |||
8 | G. nephrostoma | – | 1 | 0.20 | 0.23 | 0.16 | 0.17 | 0.17 | 0.13 | 0.12 | ||
9 | G. xesta | 0.11 | 3 | 0.17 | 0.18 | 0.13 | 0.12 | 0.13 | 0.09* | 0.07* | 0.03* |
We previously described the first informal group of Bornean Georissa, the “scaly” group which consists of 13 species (
General conchological description of a “non-scaly” group representative. Protoconch. Colour (in living or freshly dead specimens): white, yellowish green, orange, red, or brown. Sculpture pattern: smooth (no sculpture on the protoconch), straight lines (the sculpture is raised in a pattern of straight lines), rounded to ellipsoidal (the sculpture is rounded and/or ellipsoidal), mixed (a combination of more than one sculpture patterns), or irregular (the present sculpture comprises of no uniform shape or pattern). Teleoconch. Colour (in living or freshly dead specimens): white, yellowish green, orange, red, or brown. First and subsequent whorls: convex (the whorls are partially circular in shape), rounded (the whorls are semi-circular in shape), and/or flat. Suture: deeply impressed. Shoulder: narrow or extended. Number of whorls: 2 ¼–3 ½. Shell height (SH): 0.62–2.23 mm. Shell width (SW): 0.60–1.82 mm. Shell index (SI=SH/SW): 0.97–1.51. Shell sculpture. Radial sculpture: absent or present; if present then either raised in wavy and/or regular form, with narrow or wide interval. Growth lines: weak or strong, for species without clear formation of radial sculpture. Species with radial sculpture normally do not have clear growth lines since these are covered by the radial sculpture; such species generally have a row of nodules at the shoulder close to and parallel to the suture or away from the suture on the whorls. Spiral sculpture: absent, weak or strong, continuous or discontinuous, frequently the orientation is distorted by the radial sculpture (if present). Columella. Smooth and translucent. Umbilicus: open or closed. Aperture. Shape: semi-elliptic, ovoid or rounded, with straight, concave or convex parietal side, palatal edge either contiguous with the body whorl or with the parietal side. Aperture height (AH): 0.31–1.07 mm. Aperture width (AW): 0.33–1.09 mm. Aperture index (AI = AH/AW): 0.81–1.02. Peristome. Simple, thickened inside, sharp toward the edge of the aperture. Operculum. Shape: ovoid to rounded, the inner surface of the operculum has a small crater-like structure next to the peg. Peg: straight or curved. The shell dimensions of the “non-scaly” Georissa are summarised in Suppl. material
All species of Bornean Georissa have a broadly developed callus that fully covers the umbilicus, except G. leucococca, which has this callus incompletely developed. Hence, the umbilical region of this species is partially open. Georissa nephrostoma is the only known Bornean Georissa with a ‘bulb’-like callus covering the umbilical region. This is an inflation of the columella along the parietal wall. As a result, the aperture of G. nephrostoma is partly obstructed, unlike any other aperture of the Bornean Georissa. Of all the “non-scaly” Georissa, the operculum is available, except for G. corrugata, G. williamsi, and G. leucococca.
Habitat and ecology. Like the “scaly” group, the members of the “non-scaly” group Georissa are usually restricted to limestone areas. They can be found on the limestone walls, rocks located in wet and shaded environments, and occasionally at a low density on dry limestone walls and rocks, in the vegetation away from the limestone (e.g., G. gomantonensis), on other, non-limestone rocky substrates (e.g., G. saulae), and on limestone walls inside cave systems with partial or no exposure to the sunlight (e.g., G. silaburensis and G. filiasaulae).
Distribution. We provide distribution maps of the “non-scaly” Georissa of Malaysian Borneo in Figures
Remark. For the type material that was not examined during this study, there is a note in each of the species treatment that the type specimen was not seen.
In the following systematic descriptions of the “non-scaly” Georissa, the species treatment is arranged partly based on the molecular phylogeny (Fig.
Georissa borneensis
Smith, 1895: 126, plate IV fig. 18;
Gomanton, N.E. Borneo.
Lectotype (Designation by
The types specimens of the “non-scaly” Georissa of Borneo from
A Maximum likelihood phylogenetic reconstruction with ultrafast bootstrapping (5000 replicates) B bayesian phylogenetic reconstruction with posterior probabilities, constructed using MrBayes analysis. Phylogenetic analyses were conducted using concatenated sequence alignments of partial 16S and CO1 mtDNA. The analyses consist of 69 ingroup taxa (11 taxa representing the “scaly” group and 58 taxa representing the “non-scaly” group), and Bathynerita naticoidea as an outgroup. “Scaly” taxa in the phylogenies are with the red branches.
N. Borneo:
Georissa borneensis Smith, 1895. A–K
Protoconch. Colour: white to pale orange, darker than the rest of the shell. Sculpture pattern: irregular sculpture pattern, from base to apex end with no specific sculptural shape. Mesh width: 2.5–8.0 µm. Teleoconch. Colour: white to pale orange. First whorl: flat, convex close to the suture. Subsequent whorls: flat, convex and angular at the periphery. Suture: clearly impressed. Shoulder: narrow. Number of whorls: 2 ¾–3 ½. SH: 1.91–2.23 mm. SW: 1.65–1.82 mm. SI: 1.12–1.28. Shell sculpture. Radial sculpture: present, weak or flattened, densely sculpted on the whorls, ca. two to three ribs per 0.1 mm. Spiral sculpture: present, but thin and weak, only visible under high magnification (> ×100 magnification), strongest at the first whorl, weaker at subsequent whorls. Aperture. Shape: semi-elliptic, straight parietal side, palatal edge contiguous with the body whorl, palatal side tilted and angular, basal side convex. AH: 0.82–1.07 mm. AW: 1.00–1.09 mm. AI: 0.75–1.02.
The flat whorls that are strongly convex at the periphery, giving the shell an angular shape, are diagnostic. The sculpture of G. borneensis resembles that of G. similis and G. corrugata, but is weaker and more flattened than in those species. The spiral sculpture of G. corrugata is also more irregular. The adult shell G. borneensis is larger than in adult G. similis and G. corrugata. Additonally, the base to apex end sculpture of the protoconch of G. borneensis is distinct compared to these species (G. similis has a rounded protoconch sculpture and G. corrugata has straight-line protoconch sculpture).
The species is known only from Gomantong hill in the Kinabatangan region of Sabah.
The identification of G. borneensis can be confusing when we refer to the sketches by
Batu Tomanggong, Kinabatangan valley, Sandakan, Sabah, Malaysia (05°31.86'N, 118°18.24'E).
Holotype. Batu Tomanggong, Kinabatangan valley, Sandakan, Sabah, Malaysia (05°31.86'N, 118°18.24'E):
Georissa corrugata
sp. n. A–C Holotype:
The name is derived from a Latin word corrugatus, meaning “wrinkled”, referring to the coarse and irregular radial sculpture.
Protoconch. Colour: white. Sculpture pattern: parallel lines of varying width, widening before splitting in two. Mesh width: 3.1–6.2 µm, with the distance between each of the sculptural units as wide as the mesh width. Teleoconch. Colour: white. First whorl: rounded. Subsequent whorls: rounded. Suture: clearly impressed. Shoulder: narrow. Number of whorls: 2 ½–3. SH: 1.14–1.43 mm. SW: 1.01–1.11 mm. SI: 1.10–1.29. Shell sculpture. Radial sculpture: present, more prominent after the first whorl, wavy, irregular and widely spaced, often distinctly higher and strongly projected on and above the periphery. Spiral sculpture: present, regularly spaced, thin, discontinuous due the interruption by radial sculpture. Aperture. Shape: rounded to slightly ovoid, parietal side straight, palatal edge contiguous with the parietal side, palatal and basal sides convex. AH: 0.82–1.07 mm. AW: 1.00–1.09 mm. AI: 0.75–1.02. Holotype dimensions. SH: 1.71 mm, SW: 0.99 mm, AH: 0.52 mm, AW: 0.58 mm.
The wavy and irregular, widely spaced and strong radial sculpture, with thin regularly arranged spiral sculpture in between is diagnostic for G. corrugata. Georissa similis and G. borneensis have a somewhat similar arrangement of radial and spiral sculpture, but do not carry the protoconch sculpture consisting of parallel lines. The shell shape and size of G. corrugata are similar to G. similis. Besides the difference in the protoconch sculpture, the latter species also has more densely arranged radial sculpture on the teleoconch.
Georissa corrugata is distributed on the limestone hills of the lower Kinabatangan valley, known to occur from Gomantong to Batu Tomanggong, but always in low densities compared to other Georissa species. The species has also been found in the Sepulut valley, ca. a hundred km further to the southwest.
Georissa everetti
Smith, 1895: 125, plate IV fig. 15;
Rumbang, W. Sarawak.
Holotype (Holotype by original monotypy). Rumbang, Sarawak:
Kampung Giam, Lower Penrissen valley, Sarawak: JJV 12546. Kampung Benuk, Lower Penrissen valley, Sarawak (01°18.47'N, 110°17.29'E): JJV 12548. Kampung Temurang, Upper Penrissen valley, Sarawak (01°12.15'N, 110°16.18'E): JJV 12547. Great Cave, Niah National Park, Sarawak:
Georissa everetti Smith, 1895. A–K JJV 10185 A, D shell apertural view B shell side view C shell rear view E, F shell cross-section from 3D model G, H operculum frontal and ventral view from 3D model I shell top view J protoconch side view K close up of protoconch from top at 1000 × magnification. Scale bars: 500 µm (A–I); 200 µm (J); 10 µm (K).
Protoconch. Colour: orange to red. Sculpture: rounded to ellipsoidal mesh pattern, mixed with irregular sculptural shapes (whenever two or more rounded or ellipsoidal meshes are connected or combined). Mesh width: 4–30 µm. Teleoconch. Colour: orange to red. First whorl: convex. Subsequent whorls: convex, with relatively wide penultimate and final whorls. Suture: clearly impressed. Shoulder: narrow. Number of whorls: 2 ¾–3 ¼. SH: 1.82–2.23 mm. SW: 1.52–1.75 mm. SI: 1.16–1.30. Shell sculpture. Radial sculpture: present, thin, forming small nodules when intersecting with spiral sculpture; these nodules are also present on the shoulder close to the suture. Spiral sculpture: present, thin, regularly spaced, oblique, appearing immediately after the protoconch, distorted/discontinuous by radial ribs. Aperture. Shape: rounded to ovoid, straight to concave parietal side, palatal edge contiguous with the body whorl, basal side convex. AH: 1.05–0.92 mm. AW: 1.09–0.96 mm. AI: 0.89–0.99.
The strong and thin oblique spiral sculpture on its shell is diagnostic for G. everetti. Georissa similis has a somewhat similar knitted sculpture pattern resulting from the intersection of radial and spiral ribbing, but the shell shape is entirely distinct, with broad penultimate and final whorls. Based on the shell shape and habitus, G. everetti resembles G. gomantonensis and G. williamsi, which, however, have clear, regular, spiral shell ribs.
Georissa everetti is widely distributed in Sabah and Sarawak, but is found in low abundances. The species known to occur from Padawan/Penrissen, Sarawak in the South (where Rumbang, the type locality is located), to further north, Niah, Sarawak, and Sepulut valley, Sabah.
Georissa williamsi
Godwin-Austen, 1889: 353, Plate XXXIX fig. 10;
Hydrocena williamsi
(Godwin-Austen, 1889):
Georissa
sp.1 (Godwin-Austen, 1889):
Borneo.
Holotype (Holotype by original monotypy). Borneo:
Batu Punggul, Sepulut valley, Interior province, Sabah (04°39.00'N, 116°37.00'E):
Georissa williamsi Godwin-Austen, 1889. A–I
Protoconch. Colour: orange to red. Sculpture: a mix of rounded, ellipsoidal to irregular sculptural shape. Mesh width: 2–6 µm. Teleoconch. Colour: orange to red. First whorl: convex. Subsequent whorls: convex. Suture: clearly impressed. Shoulder: narrow. Number of whorls: 3–3 ¼. SH: 1.58–1.91 mm. SW: 1.17–1.42 mm. SI: 1.30–1.38. Shell sculpture. Radial sculpture: absent, only weak to strong growth lines are visible at irregular intervals. Spiral sculpture: present, thin, regularly spaced at the first whorl, appearing immediately after the protoconch, on later whorls the spiral sculpture weakens and becomes distorted by the growth lines; more than 20 spiral ribs on the body whorl of the adult individual. Aperture. Shape: semi-elliptic, straight to concave parietal side, palatal side rounded, palatal edge contiguous with the body whorl, basal side slightly convex. AH: 0.63– 0.81 mm. AW: 0.71–0.87 mm. AI: 0.89–0.95.
Georissa williamsi has a broad final whorl, in which it is similar to G. gomantonensis and G. everetti. However, these three species are all distinctly sculptured, where G. gomantonensis has raised spiral sculpture, G. everetti has oblique spiral sculpture, but G. williamsi has thin, hardly raised, and densely arranged spiral sculpture (4–6 ribs in every 0.1 mm), despite the similar shell habitus.
Georissa williamsi occurs over a large part of Sabah from the Sepulut valley in the west-central to Tawau and Lahad Datu in the east.
The type locality of G. williamsi is ‘Borneo’, with no specific location stated by
Loloposon Cave, Gunung Trus Madi, Sabah, Malaysia (05°39.00'N, 116°29.51'E).
Holotype. Loloposon Cave, Gunung Trus Madi, Sabah, Malaysia (05°39.00'N, 116°29.51'E):
Georissa trusmadi sp. n. A–C Holotype:
The species is named after the type locality, Gunung Trus Madi, Sabah.
Protoconch. Colour: orange. Sculpture pattern: rounded to irregular sculptural shape. Mesh width: 3–30 µm. Teleoconch. Colour: orange. First whorl: convex. Subsequent whorls: convex. Suture: well-impressed. Shoulder: narrow. Number of whorls: 2 ¾–3 ½. SH: 1.40–1.89 mm. SW: 1.12–1.37 mm. SI: 1.22–1.38. Shell sculpture. Radial sculpture: absent, weak growth lines present throughout the shell surface. Spiral sculpture: present, strong spiral ribs, broadly spaced above the whorls, ca. 5–7 strongly raised spiral ribs on the body whorl of the adult individual, appearing immediately after the protoconch, thin spiral ribs in between the stronger ones, more densely spaced and weaker at the basal part of the body whorl. Aperture. Shape: rounded to slightly ovoid, straight to convex parietal side, palatal edge contiguous with the parietal side, basal side convex. AH: 0.59– 0.72 mm. AW: 0.66–0.79 mm. AI: 0.85–0.91. Holotype dimensions. SH: 1.67 mm, SW: 1.28 mm, AH: 0.68 mm, AW: 0.75 mm.
Georissa trusmadi is characterised by the highly raised spiral sculpture. The number of strong spiral ribs on the first whorl is lower (3–5) than on the later whorls (5–7). The spiral sculpture is similar to G. insulae and G. hungerfordi, but always shows fewer ribs. Based on the shell habitus, it is similar to G. hungerfordi from Sarawak. The latter species, however, has the spiral ribs on the body whorl less strongly raised.
Georissa trusmadi is only known from Gunung Trus Madi, Sabah.
Georissa leucococca
Vermeulen et al., 2015: 33, fig. 19 A-B;
Malaysia, Sabah, Interior Province, Sepulut valley, Gua Pungiton (04°42.41'N, 116°36.04'E).
Type material. Holotype (Holotype by original designation). Malaysia, Sabah, Interior Province, Sepulut valley, Gua Pungiton (04°42.41'N, 116°36.04'E):
Gua Sanaron, Sepulut valley, Sabah (04°42.52'N, 116°36.16'E): JJV 8068. Gua Pungiton, Sepulut valley, Sabah: BOR/MOL 61. Gua Madai, Tawau province, Sabah (04°44.00'N, 118°8.00'E): JJV 1736. Batu Temurung, Sepulut valley, Sabah (04°42.45'N, 116°34.40'E): JJV 12681. Clearwater Cave, Mulu National Park, Sarawak: JJV 13098. Bukit Sarang group, Lower Tatau River valley, Sarawak: JJV 12571, JJV 12848, JJV 12849. Gunung Segu near Kampung Benuk, Penrissen valley, Sarawak (01°18.47'N, 110°17.29'E): JJV 12569. Bt. Krian, Upper Penrissen valley, Sarawak (01°12.20'N, 110°21.54'E): JJV 14217. Kampung Semedang, Lower Penrissen valley, Sarawak (01°17.49'N, 110°16.24'E): JJV 14221. Gunung Aup, Bau, Sarawak (01°21.36'N, 110°4.04'E): JJV 12570. Gunung Rapih, Bau, Sarawak (01°23.15'N, 110°8.29'E): JJV 12572 (Fig.
Georissa leucococca Vermeulen et al., 2015. A–I JJV 12572 A, D shell apertural view B shell side view C shell rear view E, F shell cross-section from 3D model G shell top view H protoconch side view I close up of protoconch from top at 1000 × magnification. Scale bars: 500 µm (A–G); 200 µm (H); 10 µm (I).
Protoconch. Colour: white. Sculpture pattern: minutely formed, a mix of rounded, semi-elliptic to ellipsoidal. Mesh width: 1–2 µm. Teleoconch. Colour: white. First whorl: convex. Subsequent whorls: convex. Suture: well-impressed. Shoulder: narrow. Number of whorls: 2 ¼. SH: 0.62–0.72 mm. SW: 0.60–0.70 mm. SI: 0.97–1.06. Shell sculpture. Radial sculpture: absent, only weak growth lines at irregular intervals are visible. Spiral sculpture: present, thin, regularly spaced, appearing immediately after the protoconch, distorted by the growth lines, more prominent at the upper whorls, becoming weaker when closer to the columellar region. Aperture. Shape: semi-elliptic, straight to concave parietal side, palatal side rounded, palatal edge contiguous with the body whorl, basal side convex. Umbilicus: open, with a narrow space underneath the reflected columellar peristome. AH: 0.31– 0.37 mm. AW: 0.33–0.38 mm. AI: 0.87–0.97.
Georissa leucococca has spiral sculpture that is more prominent at the upper part of the whorls, similar to G. bangueyensis. Georissa leucococca is so far the only known Bornean Georissa with an open umbilicus and with an adult shell size of hardly more than 1 mm. It has an angular shell shape, similar to G. borneensis.
Georissa leucococca is widely distributed in Malaysian Borneo. The species is known to occur from west Sarawak to east Sabah.
Georissa hungerfordi Godwin-Austen, 1889: 354, Plate XXXIX, fig. 9.
Georissa lowi Smith, 1893: 351.
Georissa williamsi
Godwin-Austen:
Borneo.
Lectotype (Designation by
Rumbang, Sarawak:
Georissa hungerfordi Godwin-Austen, 1889. A–K
Protoconch. Colour: orange. Sculpture pattern: smooth. Teleoconch. Colour: orange. First whorl: convex. Subsequent whorls: convex, shell shape slender to broad. Suture: well-impressed suture, straight to slightly concave, and narrow shoulder. Number of whorls: 2 ½–3 ¼. SH: 1.35–1.85 mm. SW: 1.38–1.20 mm. SI: 1.16–1.36. Shell sculpture. Radial sculpture: absent, only weak to strong growth lines present throughout the shell surface. Spiral sculpture: present, strong spiral ribs, regularly spaced, with ca. 7–10 spiral ribs on the body whorl of the adult individual, appearing immediately after the protoconch, sometimes distorted/discontinuous by growth lines, more densely spaced spiral cords at the basal part of the body whorl. Aperture. Shape: rounded to slightly ovoid, straight to concave parietal side, palatal edge contiguous with the body whorl, basal side convex. AH: 0.63– 0.79 mm. AW: 0.67–0.83 mm. AI: 0.89–1.06.
Georissa hungerfordi is characterised by the strong spiral sculpture with ca. 7–10 spiral ribs on the body whorl. The shell shape approaches the shape of G. trusmadi and G. pachysoma. Georissa hungerfordi has stronger spiral sculpture compared to G. pachysoma but weaker compared with G. trusmadi. The spiral ribbings resemble G. insulae, which has, however, a more elongated and slender shell shape.
Georissa hungerfordi is distributed from Bau to Padawan/Penrissen, Kuching, Sarawak.
ML and Bayesian analyses show that the samples of G. hungerfordi (16S: n = 14; CO1: n = 11) form a monophyletic group with 100% BS and 100% PP, sister group to the “scaly” group, except G. saulae.
Georissa gomantonensis
Smith, 1893: 351, Plate XXV fig. 25;
Georissa gomantongensis
Smith:
Gomanton, N. Borneo.
Holotype (Holotype by original monotypy). Gomanton, N. Borneo:
Gua Gomantong, Kinabatangan, Sabah (05°32.00'N, 118°06.00'E): BOR/MOL 7632, BOR/MOL 7389 (Fig.
Georissa gomantonensis Smith, 1893. A–K BOR/MOL 7389 A, D shell apertural view B shell side view C shell rear view E, F shell cross-section from 3D model G, H operculum frontal and ventral view from 3D model I shell top view J protoconch side view K close up of protoconch from top at 1000 × magnification. Scale bars: 500 µm (A–I); 200 µm (J); 10 µm (K). Shell view image (Fig.
Protoconch. Colour: greenish yellow. Sculpture: ellipsoidal mesh to irregular sculptural shape. Mesh width: 4–16 µm. Teleoconch. Colour: greenish yellow. First whorl: convex. Subsequent whorls: convex. Suture: well-impressed. Shoulder: slightly extended, with a row of regularly spaced granules. Number of whorls: 3–3 ¼. SH: 1.95–2.17 mm. SW: 1.67–1.68 mm. SI: 1.17–1.29. Shell sculpture. Radial sculpture: absent, only weak growth lines present throughout the shell surface. Spiral sculpture: present, strongly sculpted spiral ribs, at regular intervals, appearing immediately after the protoconch, sometimes distorted/discontinuous by growth lines, reduced in strength when reaching the columellar region, ca. 14–18 spiral ribs visible on the body whorl in the adult individual. Aperture. Shape: rounded to slightly ovoid, straight to concave parietal side, palatal edge contiguous with the body whorl, basal side convex. AH: 0.94– 0.97 mm. AW: 1.04–1.08 mm. AI: 0.87–0.92.
Georissa gomantonensis is characterised by its bright greenish yellow colour, broad final whorl, and strong spiral sculpture. The spiral sculpture pattern is similar to G. insulae, but the shell habitus of G. gomantonensis is much broader and inflated. Georissa everetti and G. williamsi have a similar shell habitus as G. gomantonensis, but differ because lacking of the oblique (G. everetti) and densely arranged (G. williamsi) spiral sculpture.
Georissa gomantonensis is widely distributed throughout Sabah. More commonly found in the vegetation of the limestone forest, rather than on the limestone rocks themselves.
ML and Bayesian analyses show that the individuals of G. gomantonensis (16S: n = 2; CO1: n = 2) form a monophyletic group with 100% BS and 100% PP, sister group to the paraphyletic G. saulae + G. filiasaulae.
Georissa filiasaulae
Haase & Schilthuizen, 2007: 216, figs 2A–B and 2E;
Malaysia, Sabah, Sepulut valley, Interior province, Batu Sanaron (04°42.05'N, 116°36.01'E).
Holotype (Holotype by original designation). Malaysia, Sabah, Sepulut valley, Interior province, Batu Sanaron (04°42.05'N, 116°36.01'E): BOR/MOL 3795. Paratypes. Malaysia, Sabah, Sepulut valley, Interior province, Batu Sanaron (04°42.05'N, 116°36.01'E): BOR/MOL 3491 (7); ZMB 107143-107149 (7) (not seen).
Batu Sanaron, Interior province, Sepulut valley, Sabah: BOR/MOL 532, BOR/MOL 3405. Batu Pungiton, Interior province, Sepulut valley, Sabah Batu Pungiton, Sabah (04°42.41'N, 116°36.04'E): BOR/MOL 12768 (Fig.
Georissa filiasaulae Haase & Schilthuizen, 2007. A–K BOR/MOL 12768 A, D shell apertural view B shell side view C shell rear view E, F shell cross-section from 3D model G, H operculum frontal and ventral view from 3D model I shell top view J protoconch side view K close up of protoconch from top at 1000 × magnification. Scale bars: 500 µm (A–I); 200 µm (J); 10 µm (K).
Protoconch. Colour: white. Sculpture: a mix of rounded, ellipsoidal to irregular sculptural shape. Mesh width: 2.5–20 µm. Teleoconch. Colour: white. First whorl: convex. Subsequent whorls: convex, shell shape slender to broad. Suture: clearly impressed. Shoulder: slightly extended, regularly spaced nodules. Number of whorls: 2 ½–3. SH: 1.21–1.68 mm. SW: 1.67–1.68 mm. SI: 1.08–1.27. Shell sculpture. Radial sculpture: absent, weak to strong growth lines. Spiral sculpture: present, rather weak and thin, densely spaced on the first whorl, the ribbing appears immediately after the protoconch, sometimes distorted/discontinuous by the growth lines, superficially smooth on the later whorls. Aperture. Shape: rounded to semi-elliptic, straight to slightly convex parietal side, palatal side rounded, palatal edge partially contiguous with the body whorl and parietal side, basal side convex. AH: 0.67– 0.79 mm. AW: 0.69–0.83 mm. AI: 0.93–0.97.
Georissa filiasaulae has weak, thin, and densely arranged spiral sculpture with nodular structure on the shoulder. The shell colour and thickness are most similar to G. corrugata, which has white and partially transparent shell.
Georissa filiasaulae is a cave specialist, known from the cave system of Batu Sanaron and Batu Tinahas in the Sepulut valley.
ML and Bayesian analyses of G. filiasaulae (16S: n = 3; CO1: n = 3) show that G. filiasaulae form one clade with 98% BS and 100% PP. The sister group is the G. saulae population from Pungiton (G. saulae is paraphyletic).
Georissa filiasaulae is one of the two known Bornean Georissa that is troglobitic.
Georissa williamsi
Godwin-Austen:
Pulau Mantanani Besar, Sabah, Malaysia (06°43.06'N, 116°20.50'E).
Holotype. Pulau Mantanani Besar, Sabah, Malaysia (06°43.06'N, 116°20.50'E):
Georissa insulae sp. n. A–C Holotype:
The name is a genitive singular of the Latin word insula, meaning ‘island’, which refers to the Mantanani islands, the main collecting locality.
Protoconch. Colour: orange. Sculpture pattern: a mix of rounded and ellipsoidal sculpture. Mesh width: 1.5–12.0 µm. Teleoconch. Colour: orange. First whorl: convex. Subsequent whorls: convex. Suture: well-impressed. Shoulder: narrow. Number of whorls: 2 ¾–3 ¼. SH: 1.78–2.11 mm. SW: 1.21–1.40 mm. SI: 1.42–1.51. Shell sculpture. Radial sculpture: absent, weak growth lines present throughout the shell surface. Spiral sculpture: present, strong, regularly spaced, ca. 10–12 spiral ribs on the body whorl of the adult individual, developed immediately after the protoconch; more densely spaced spiral ribs at the basal part of the body whorl, becoming weaker closer to the columellar region. Aperture. Shape: rounded to slightly ovoid, straight to concave parietal side, palatal edge contiguous with the body whorl, basal side convex. AH: 0.66–0.79 mm. AW: 0.74–0.84 mm. AI: 0.89–0.94. Holotype dimensions. SH: 2.11 mm, SW: 1.40 mm, AH: 0.79 mm, AW: 0.84 mm.
Georissa insulae is characterised by the strong and regularly spaced spiral ribs throughout the entire shell. This shell sculpture is similar to that of G. hungerfordi and G. trusmadi, but less raised than in these two species. Georissa insulae has a greater number of spiral ribs, ca. 10–12 ribs on its shell compared to these two species. The shell habitus is distinctly elongated compared to other spirally ribbed Bornean Georissa.
Known from islands of Mantanani Kecil, Mantanani Besar, Lungisan, and on the mainland from Pitas to Kinabalu National Park, Sabah.
ML and Bayesian analyses of G. insulae (16S: n = 4) show that G. filiasaulae form one clade with 100% BS and 100% PP. Sister to the rest of “non-scaly” Georissa, except for G. hungerfordi + G. gomantonensis + G. filiasaulae.
Georissa pachysoma Vermeulen & Junau, 2007: 216, fig. 7.
Malaysia, Sarawak, 2nd div.: Lower Tatau River valley, Bukit Sarang group, Bukit Lebik.
Holotype (Holotype by original designation). Malaysia, Sarawak, 2nd div.: Lower Tatau River valley, Bukit Sarang group, Bukit Lebik:
Georissa pachysoma Vermeulen & Junau, 2007. A–K
Bukit Sarang group, Lower Tatau River valley: JJV 12626, JJV 12844, JJV 12845, JJV 12846. Upper Tatau River valley, upper Kakus River limestone scarps: JJV 12847. Bt. Besungai 0.5 m SW of Batu Gading, Long Lama, Baram valley (03°52.00'N, 114°25.00'E): JJV 4940. Slopes and cliffs along path to Great Cave, Niah National Park: JJV 10216. N side of limestone area, Painted Cave, Niah National Park: JJV 10391. Bukit Lebik and Bukit Anyi, Bukit Sarang, Bintulu, Sarawak (02°39.31'N, 113°02.47'E):
Protoconch. Colour: red to brown. Sculpture: a mix of triangular, rounded, and irregular sculptural shapes. Mesh width: 2–12 µm. Teleoconch. Colour: red to brown. First whorl: convex. Subsequent whorls: convex, broad at the final whorl. Suture: clearly impressed. Shoulder: narrow. Number of whorls: 2 ¾–3 ¼. SH: 1.20–1.65 mm. SW: 0.95–1.23 mm. SI: 1.19–1.34. Shell sculpture. Radial sculpture: absent, weak growth lines at irregular intervals only. Spiral sculpture: present, rather thin, widely spaced in the centre of the whorls, densely spaced close to the suture and the periphery, ribs appear immediately after the protoconch, ca. 12–15 medium raised spiral ribs, distorted/discontinuous where they are crossed by the growth lines. Aperture. Shape: rounded to semi-elliptic, straight to concave parietal side, palatal side convex and tilted below, palatal edge contiguous with the body whorl, basal side convex. AH: 0.54– 0.70 mm. AW: 0.57–0.72 mm. AI: 0.90–1.00.
Georissa pachysoma is characterised by a dark red to brown colour of the shell, similar to G. nephrostoma, but the latter species has wavy spiral ribs while G. pachysoma does not. In shell habitus, G. pachysoma closely resembles G. hungerfordi, but the colour and spiral sculpture of G. hungerfordi (orange in colour in living or freshly dead specimens, with highly raised spiral sculpture) is entirely different from G. pachysoma.
Georissa pachysoma is widely distributed from Bukit Sarang, Bintulu to further north in Baram and Niah, Sarawak.
ML and Bayesian analyses of G. pachysoma (16S: n = 4; CO1: n = 4) show that G. pachysoma forms one clade with 100% BS and 100% PP, sister to the rest of the “non-scaly” group species, except for G. hungerfordi + G. gomantonensis + G. filiasaulae + G. insulae.
Georissa similis
Smith, 1893: 351, Plate XXV fig. 26;
Georissa
sp. 3 (Smith, 1893):
Gomanton Hill, N. Borneo.
Lectotype (Designation by
Gomanton, N. Borneo:
Georissa similis Smith, 1893. A–K
Protoconch. Colour: red. Sculpture: rounded to ellipsoidal mesh pattern. Mesh width: 2.8–7.0 µm. Teleoconch. Colour: red. First whorl: convex to flat at the upper part of the whorl. Subsequent whorls: convex. Suture: clearly impressed. Shoulder: narrow to slightly extended. Number of whorls: 2 ½–3 ¼. SH: 0.96–1.44 mm. SW: 0.85–1.06 mm. SI: 1.13–1.36. Shell sculpture. Radial sculpture: present, dense and regularly spaced, always stronger than the spiral sculpture. Spiral sculpture: present, raised but thin, appearing immediately after the protoconch, spiral sculpture often interrupted due to highly developed radial ribs; the overlapping radial and spiral sculptures form knitted structures on the shell. Aperture. Shape: semi-elliptic to rounded, straight to slightly concave parietal side, palatal edge contiguous with the parietal side, basal side convex. AH: 0.49– 0.64 mm. AW: 0.50–0.67 mm. AI: 0.85–0.98.
Georissa similis is characterised by the dense radial sculpture. The radial ribs intersect with the thin spiral ribs and form knitted structures throughout the shell surface. The sculpture pattern is similar to G. everetti but not oblique, and the radial sculpture is more raised in G. similis. The shell shape is similar to G. corrugata and G. xesta, but these species differ entirely in their shell and protoconch sculpture (G. corrugata has irregular radial shell sculpture and straight-line protoconch sculpture; G. xesta does not have radial sculpture and the protoconch sculpture is a mix of irregular shapes).
Georissa similis is widely distributed in the east of Sabah, from Sandakan in the north to Tawau in the south and Lahad Datu in the east.
ML and Bayesian analyses of G. similis (16S: n = 5; CO1: n = 5) show that G. similis form one clade with 100% BS and 100% PP, sister to the group of G. xesta + G. nephrostoma + G. bangueyensis + G. flavescens.
Georissa xesta Thompson & Dance, 1983: 125, figs 69–70.
A small limestone ridge quarried for rock 5 mi W Kudat, Sabah, Borneo (06°57.00'N, 116°48.00'E).
Holotype (Holotype by original designation). A small limestone ridge quarried for rock 5 mi W Kudat, Sabah, Borneo (06°57.00'N, 116°48.00'E): UF 35968 (not seen). Paratypes. A small limestone ridge quarried for rock 5 mi W Kudat, Sabah, Borneo (06°57.00'N, 116°48.00'E): UF 35969 (not seen), UF35970 (not seen), SMF 255740/6 (not seen),
Kinabatangan valley, Batu Tulug (Batu Putih) along road Lahad Datu-Sandakan, N of bridge over Kinabatangan River, Sandakan province, Sabah (05°25.00'N, 117°56.00'E): JJV 1481. Kinabatangan valley, Batu Keruak 2 near Sukau, Sandakan province, Sabah (05°32.00'N, 118°18.00'E): JJV 9786. Kinabatangan valley, Batu Tomanggong Kecil, Sandakan province, Sabah (05°30.12'N, 118°18.10'E): JJV 9828. Batu Tomanggong Besar, Kinabatangan valley, Sandakan, Sabah (05°31.02'N, 118°18.21'E): BOR/MOL 1437, BOR/MOL 2252, BOR/MOL 2281. Batu Tomanggong Besar 2, Kinabatangan valley, Sandakan, Sabah (05°31.16'N, 118°18.33'E): BOR/MOL 1440. Batu Tomanggong Kecil, Kinabatangan valley, Sandakan, Sabah (05°30.21'N, 118°18.18'E): BOR/MOL 2025, BOR/MOL 2053. Batu Keruak, Kinabatangan valley, Sandakan, Sabah (05°32.00'N, 118°18.00'E): BOR/MOL 2687. Lower Kinabatangan valley, Sabah; Unnamed limestone hill 1 (05°31.11'N, 118°17.23'E): BOR/MOL 2151, BOR/MOL 2184, BOR/MOL 2217; Unnamed limestone hill 2 (05°30.00'N, 118°17.00'E): BOR/MOL 1441. Batu Materis, Kinabatangan valley, Sabah (05°31.21'N, 118°01.31'E): BOR/MOL 2113, BOR/MOL 2083. Bod Tai, Kinabatangan valley, Sabah (05°31.00'N, 118°13.00'E): BOR/MOL 1443. Bukit Mawas, lower Kinabatangan valley, Sabah: BOR/MOL 1444. Pangi, Kinabatangan valley, Sandakan province, Sabah (05°31.59'N, 118°18.43'E): BOR/MOL 1442. Ulu Sungai Resang, lower Kinabatangan valley, Sabah (05°31.00'N, 118°21.00'E): BOR/MOL 1438, BOR/MOL 7303 (Fig.
Georissa xesta Thompson & Dance, 1983. A–K BOR/MOL 7303 A, D shell apertural view B shell side view C shell rear view E, F shell cross-section from 3D model G, H operculum frontal and ventral view from 3D model I shell top view J protoconch side view K close up of protoconch from top at 1000 × magnification. Scale bars: 500 µm (A–I); 200 µm (J); 10 µm (K).
Protoconch. Colour: pale orange to orange. Sculpture: irregular sculptural shape resulted from a combination of rounded to ellipsoidal sculpture patterns. Mesh width: 1–10. Teleoconch. Colour: orange, the colour of the teleoconch always darker than the protoconch. First whorl: convex. Subsequent whorls: convex. Suture: clearly impressed. Shoulder: narrow to slightly extended. Number of whorls: 2 ¾–3 ½. SH: 1.05–1.68 mm. SW: 0.84–1.18 mm. SI: 1.22–1.45. Shell sculpture. Radial sculpture: absent, only weak growth lines present. Spiral sculpture: present, ca. 20–25 thin and weak spiral ribs, superficially smooth, densely arranged, appearing immediately after the protoconch, distorted by growth lines. Aperture. Shape: rounded to slightly ovoid, straight to concave parietal side, palatal edge partially contiguous with the body whorl and the parietal side, basal side convex. AH: 0.48– 0.66 mm. AW: 0.50–0.74 mm. AI: 0.76–0.98.
Georissa xesta has densely arranged spiral sculpture (8–10 ribs in every 0.1 mm), unlike G. bangueyensis (4–5 ribs in every 0.1 mm), which has more space in between the spiral ribs. The shell of G. xesta looks superficially smooth under a stereomicroscope at low contrast with less than × 20 magnification. The dense spiral sculpture is similar to the spiral ribbing pattern of G. williamsi, but the shell habitus of these two species is entirely different, where G. williamsi has a broad ultimate whorl but G. xesta does not. Based on the shell shape, G. xesta is similar to G. similis and G. corrugata, but both of these species have strongly raised radial sculpture.
Georissa xesta is widely distributed in Sabah, especially in the coastal areas around Kudat, Sandakan, Lahad Datu, and Tawau.
In the ML and Bayesian analyses of G. xesta (16S: n = 2; CO1: n = 3), the Materis and Ulu Resang populations form highly supported clades 96% BS and 100% PP, which are paraphyletic with respect to G. nephrostoma.
The type series of G. xesta from
Georissa nephrostoma Vermeulen et al., 2015: 34, fig. 20.
Malaysia, Sabah, Sandakan Province, Kinabatangan valley, Batu Keruak 2 near Sukau.
Holotype (Holotype by original designation). Malaysia, Sabah, Sandakan Province, Kinabatangan valley, Batu Keruak 2 near Sukau (05°32.00'N, 118°18.00'E):
Batu Keruak, Sandakan Province, Sabah (05°32.00'N, 118°18.00'E): BOR/MOL 1454,
Georissa nephrostoma Vermeulen et al., 2015. A–K
Protoconch. Colour: red to brown. Sculpture: rounded, ellipsoidal to irregular sculptural shape. Mesh width: 2–10 µm. Teleoconch. Colour: red to brown. First whorl: rounded to convex. Subsequent whorls: rounded to convex. Suture: clearly impressed. Shoulder: narrow. Number of whorls: 2 ½–2 ¾. SH: 0.87–1.24 mm. SW: 0.69–0.92 mm. SI: 1.26–1.43. Shell sculpture. Radial sculpture: absent, densely spaced weak to strong growth lines, no formation of true radial ribs. Spiral sculpture: present, appearing immediately after the protoconch; the ribs are low but narrow to broadly sculpted, regularly spaced, wavy, ca. 12–14 spiral ribs at the upper part of the body whorl; near the aperture, the spiral sculpture is weakened and flattened approaching the columellar region. Aperture. Shape: semi-elliptic, highly convex, and bulky parietal side, palatal side rounded, palatal edge contiguous with the parietal side, basal side convex. AH: 0.40–0.55 mm. AW: 0.43–0.60 mm. AI: 0.92–0.95.
Georissa nephrostoma is characterised by the wavy formation of the spiral sculpture and the inflated parietal side of the aperture. The wavy sculpture pattern of G. nephrostoma is similar to G. flavescens but the two species differ entirely based on the shell habitus, where G. flavescens has a more compressed shell habitus. In shell shape, G. nephrostoma resembles G. similis, G. xesta and G. bangueyensis, but none of these species have the uniquely inflated parietal side of the aperture.
Georissa nephrostoma is distributed from Sukau to Gomantong, Kinabatangan region, Sabah.
ML and Bayesian analyses of G. nephrostoma (16S: n = 5; CO1: n = 1) showed that all G. nephrostoma specimens form one clade with 99% BS and 100% PP. The sister group is the G. xesta population from Materis and Ulu Resang (G. xesta is paraphyletic).
Georissa bangueyensis
Smith, 1895: 125, Plate IV fig. 16;
Banguey Island, N. Borneo.
Lectotype (Designation by
Banggi Island, South end, Kudat province, Sabah (07°06.32'N, 117°5.07'E):
Georissa bangueyensis Smith, 1895. A–K
Protoconch. Colour: red. Sculpture: irregular sculptural shape to smooth. Mesh width: 1–20 µm. Teleoconch. Colour: red. First whorl: convex. Subsequent whorls: convex. Suture: clearly impressed. Shoulder: narrow. Number of whorls: 2 ¾–3. SH: 1.00–1.33 mm. SW: 0.77–0.96 mm. SI: 1.22–1.42. Shell sculpture. Radial sculpture: absent, only weak growth lines are here and there visible. Spiral sculpture: present, appearing immediately after the protoconch, regularly arranged; ca. 8–10 spiral ribs on the first whorl, on the later whorls the sculpture is more prominent at the upper part of the whorl, weaker and flattened closer to the columellar region. Aperture. Shape: semi-elliptic to rounded, straight to slightly concave parietal side, palatal edge contiguous with the parietal side, basal side convex. AH: 0.40– 0.53 mm. AW: 0.45–0.60 mm. AI: 0.81–1.00.
Georissa bangueyensis is characterised by its clear spiral ribs at the upper part of the body whorl, similar to G. flavescens and G. nephrostoma, but the two latter species have wavy spiral ribs. Spiral sculpture on the lower whorl is weaker and less obvious closer to the columellar region. In shell sculpture, it is most similar to G. xesta, but the latter species has more densely arranged spiral sculpture (see discussion in G. xesta).
Georissa bangueyensis is widely distributed in the coastal regions of northern and eastern Sabah.
ML and Bayesian analyses of G. bangueyensis (16S: n = 6; CO1: n = 6) show that G. bangueyensis forms a monophyletic clade with 100% BS and 100% PP, and is sister to G. flavescens.
Georissa flavescens
Smith, 1895: 126, Plate IV fig. 17;
Gomanton, N.E. Borneo.
Lectotype (Designation by
Tomanggong Besar 1, Kinabatangan, Sabah: BOR/MOL 7299. Tomanggong Besar 2, Kinabatangan, Sabah: BOR/MOL 7626. Batu Pangi, Kinabatangan valley, Sandakan province, Sabah (05°31.59'N, 118°18.43'E): JJV 9827, BOR/MOL 7288 (Fig.
Georissa flavescens Smith, 1895. A–K BOR/MOL 7288 A, D shell apertural view B shell side view C shell rear view E, F shell cross-section from 3D model G, H operculum frontal and ventral view from 3D model I shell top view J protoconch side view K close up of protoconch from top at 1000 × magnification. Scale bars: 500 µm (A–I); 200 µm (J); 10 µm (K).
Protoconch. Colour: orange. Sculpture: rounded, ellipsoidal to irregular sculptural shape. Mesh width: 2–10 µm. Teleoconch. Colour: orange. First whorl: convex. Subsequent whorls: convex, and slightly angular at the penultimate whorl. Suture: clearly impressed. Shoulder: narrow to slightly extended. Number of whorls: 2 ½–2 ¾. SH: 0.87–1.20 mm. SW: 0.73–0.95 mm. SI: 1.15–1.26. Shell sculpture. Radial sculpture: absent, weak growth lines. Spiral sculpture: present, appearing immediately after the protoconch, wavy, thin, and regularly arranged ribs at the first whorl, more raised at the later whorls. Aperture. Shape: semi-elliptic, straight to concave parietal side, palatal side rounded, palatal edge contiguous with the palatal side, basal side convex. AH: 0.43– 0.55 mm. AW: 0.47–0.58 mm. AI: 0.82–0.95.
Georissa flavescens is characterised by the wavy spiral sculpture, which it only shares with G. nephrostoma, but the latter species, with its narrow spire and inflated columella, is entirely distinct in shell habitus. The shell shape of G. flavescens is similar to G. gomantonensis, G. williamsi, and G. everetti, but its size is reduced compared to these three species.
Georissa flavescens is restricted to four limestone hills, Batu Pangi, Batu Keruak, Batu Gomantong, and Batu Tomanggong, in the Lower Kinabatangan valley of Sabah.
ML and Bayesian analyses of G. flavescens (16S: n = 7; CO1: n = 8) show that G. flavescens forms a monophyletic clade with 100% BS and 100% PP, a sister species of G. bangueyensis.
We thank Francisco Borrero and Carl Christensen for their valuable comments and suggestions that improved the manuscript. We thank the malacology curators of
An overview of scanning parameters of each "non-scaly" Georissa
Data type: table
Shell measurement of the "non-scaly" Georissa
Data type: measurement data